1. Field of the Invention
This invention relates to a novel class of organic nitriles which exhibit potent antifeeding activity toward the fall armyworm, Spodoptera frugiperda (J. E. Smith), and European corn borer, Ostrinia nubilalis (Hubner).
2. Summary of the Prior Art
Allomones are described by Schoonhoven [In Semiochemicals, Donald A. Nordlun, Richard L. Jones, and W. Joe Lewis (eds.), p. 31 ff., John Wiley & Sons (1981)] as chemical mediators produced by plants which protect them from insects. Allomones may or may not be toxic to insects, but they deter or inhibit the feeding of insects on the plant by activating deterrent sensitive receptors in the insect.
The search for natural pest control agents has extended into many plant species and resulted in the isolation and, in some cases, identification of feeding deterrents or allomones of varied chemical structure.
For example, Mikolajczak and Reed reported the study of 22 species of plants from the Meliaceae family [J. Chem. Ecol. 13(1): 99 (1987); see also Mikolajczak et al., J. Chem. Ecol. 15(1): 121 (1989)]. Seed extracts were tested for antifeedant activity and toxicity against the fall armyworm and striped cucumber beetle. A number of the extracts were comparable in activity to neem preparations which contain azadirachtin, a semi-commercial allomone [see J. D. Warthen, Jr., USDA Agricultural Reviews and Manuals, ARM-NE-4, 21 pp. (1979)].
Kubo et al. [J. Chem. Soc., Chem. Commun. 1976: 1013 (1976)] isolated potent armyworm antifeedants from East African Warbergia plants. These were characterized as bicyclic dialdehyde structures polygodial, ugandensidial, and warberganal.
Myricoside, another armyworm antifeedant, was reported to be a complex polycyclic compound by Cooper et al. [J. Am. Chem. Soc. 102(27): 7953 (1980)].
Mikolajczak and Weisleder [J. Nat. Prod. 51(3): 606 (1988)] isolated a limonoid antifeedant for the fall armyworm.
Certain indole compounds are known to exert biological effects upon insects. Smissman et al. [Science 133: 462 (1961)] reported that indole-3-acetonitrile which was isolated from cabbage plants inhibited the growth of Pyrausta mibelalis (Hbn.). Indole-3-acetic acid, a closely related structure, did not inhibit insect growth under the same assay conditions.
Luis J. Corcuera [Phytochemistry 23(3): 539-541 (1984)] found that several indole alkaloids from Gramineae showed feeding deterrent activity on aphids at low concentrations. These compounds are 3-N,N-dimethylaminomethylindole derivatives.
Takasugi et al. [Bull. Chem. Soc. Jpn. 61: 285 (1988)] and Dahiya and Rimmer [Phytochemistry 27(10): 3105 (1988)] have reported the isolation of sulfur-containing indole phytoalexins from the Chinese cabbage.
Phenyl-dimethylmercaptoacetonitrile, compound 10 of this invention, was previously prepared by Marchand et al. [C.A. 92: P616 (1980)]; no biological activity of any sort was reported for this material.